Surfactant mixture

ABSTRACT

A surfactant composition is described. This composition is used for the emulsification of oil and water to form microemulsions. These microemulsions can be used as industrial lubricants e.g. machine tool cutting oils (although many uses are possible) and show distinct advantages over traditional neat oils or macroemulsions.

[0001] This invention relates to a surfactant mixture for use in preparing industrial lubricants e.g. hydraulic or machine tool cutting oils comprising clear homogenous microemulsions.

[0002] The use of cutting oil and macroemulsions of these oils in metalworking is well known. Neat oils are used when a good surface finish is required on the metal being worked. However, due to the poor coolant properties of the oils used rapid degeneration of the machine tool (which can reach temperatures in excess of 200° C.) takes place.

[0003] To improve the life of the machine tool macroemulsions of the oil are made with water. The excellent coolant properties of the water does indeed improve the life of the tool. However, the incorporation of water coupled with the instability of macroemulsions gives rise to several other problems. These are that the lubricity of the oil is decreased with addition of water thereby affecting the surface finish of the metal. Also, as water is present the likelihood of corrosion becomes apparent. Consequently, the macroemulsion requires further addition of specialist additives to overcome the occurrence of corrosion. The presence of water droplets (>0.1 μm) may also give rise to bacterial growth which not only can affect performance of the lubricant but also is unpleasant for the machine operator due to the oil becoming rancid and thus foul smelling.

[0004] The present invention seeks to overcome the above mentioned problems by providing a surfactant composition which allows the formulation of oil-water mixtures which are microemulsions of water in oil and are true solutions or behave as such. The term “solution” herein describes any mixtures which are clear and homogenous. The term “behave as such” means that the mixture has substantially the same stability as a solution.

[0005] The present invention accordingly provides a composition for use in combining oil and water as a stable solution (emulsion, preferably a microemulsion) which composition comprises (a) a fatty acid amine ethoxylate (b) a C₆-C₁₅ alcohol ethoxylate and optionally (c) a tall oil fatty acid amine.

[0006] The components of the composition are combined together in quantities that allow the formation of microemulsions on addition to the appropriate oil and water mixture.

[0007] The composition may comprise additional components. These have been found to include sorbitan esters, mono and di-glycerides of fatty acids, polymeric emulsifiers containing fatty acid side groups, polyimides and substituted polyimides such as poly isobutenylsuccimide. Other surfactant types will be apparent to those versed in the art.

[0008] Preferred components of the surfactant composition are all readily available commercially.

[0009] A preferred embodiment of the invention comprises the following components:

[0010] i) 1-5 parts of a fatty acid amine ethoxylate

[0011] ii) 0.5-4 parts of alcohol ethoxylate and optionally

[0012] iii) 1.5-5 parts of tall oil fatty acid amine

[0013] the parts by volume in each case being relative to the total volume of the composition.

[0014] In a highly preferred embodiment, the composition of the present invention comprises the tall oil fatty acid amine. This component may be used to impart (further) stability to the composition of the present invention.

[0015] The minimum quantity of the surfactant composition required is dependant upon the water content of the desired microemulsion and the base oil type being used. For example, 80 parts of a naphthenic base oil (Shell, solvent pale 60) was emulsified with 20 parts of water such that a microemulsion was obtained. This was achieved with the addition of 20 parts of the surfactant composition. Using a different base oil, based upon a paraffinic type (Shell, 130 solvent neutral), with the same quantities of water and oil required 30 parts of the surfactant composition to form a microemulsion.

[0016] To determine the minimum quantity of the surfactant composition required the surfactant is added to the oil water mixture with gentle mixing until a clear homogenous microemulsion is obtained.

[0017] These microemulsions will have many applications in the industrial lubricants market. It may be necessary for certain applications to incorporate other additives i.e. to give extreme pressure protection for higher temperature applications. These applications and additional additives will be apparent to those skilled in the art.

[0018] The invention shall now be described by way of example only.

EXAMPLE 1

[0019] A composition suitable for combining 70 parts of a paraffinic type base oil (Shell 130 solvent neutral) with 30 parts of water was prepared by adding the following components in the quantities stated:

[0020] 3 parts fatty acid amine ethoxylate

[0021] 2.75 parts tall oil fatty acid amine

[0022] 2 parts C₆-C₁₅ alcohol ethoxylate

[0023] The components were gently mixed to form a homogenous solution.

EXAMPLE 2

[0024] 30 ml of water was added to 70 m of Shell 130 solvent neutral in a clear glass container. The surfactant composition of Example 1 was introduced to the oil and water from a burette. After each addition of surfactant the resulting solution was mixed. This continued until a clear homogenous solution was observed. The resulting solution remains stable for more than one year.

EXAMPLE 3

[0025] 20 ml of water was added to 80 ml of Shell solvent neutral in a clear glass container. The surfactant solution of Example 1 was introduced into the oil and water as in Example 2. The resulting solution remains stable for more than one year.

EXAMPLE 4

[0026] The solution obtained in Example 2 was used to determine its corrosive properties on mild steel. This was done by placing a piece of mild steel in the solution and observing the formation of rust. No corrosion has been observed after 6 months.

EXAMPLE 5

[0027] When using macroemulsions of oil and water problems of micro-organism growth can arise.

[0028] To determine whether the composition of the present invention is effective in preventing such growth an algae was introduced to the solution of Example 2. Any growth of this algae was to be monitored by any colour change of the solution as the algae produce a green growth in macroemulsions.

[0029] No micro-organism growth was observed after 6 months. It is believed that the compositions of the present invention prevents any micro-organism growth because the water droplets in the solution containing the surfactant composition are smaller than the micro-organisms and so there is insufficient oxygen for the algae to grow.

EXAMPLE 6

[0030] A series of tests were conducted on an industrial lathe using solutions in Examples 2 and 3 and the neat base oil (Shell 130 solvent neutral). Initially the tool bits that were to be used were prepared by grinding to the same specification. These were then electron micrographed to confirm that the tool bits were to all intents and purposes identical. The bits were then used to lathe 75 mm external diameter mild steel rod down to 20 mm external diameter over a 600 mm length at a rate of 2.5 mm per cut. The tool bits were then electron micrographed for a second time to determine which bits were wearing faster. The results, which are shown in Table 1 and FIGS. 1-10, show that bits containing just neat oil or neat oil with an extreme pressure additive (Cereclor E45) wear considerably more quickly than those of Examples 2 and 3. The surface finish of the mild steel of all the samples was compared and found to be no different, thereby indicating no loss in the lubricity of the solutions containing water.

[0031] An added benefit was also observed during this test. When lathing the steel the observable amount of smoke was reduced using the solutions of Examples 2 and 3. In addition it is believed that the emissions given by the solutions of the present invention will be cleaner due to the higher oxygen content because of the presence of water. As seen in Table 1, the swarf generated by the cutting was collected and an experiment was carried out to determine the oil that had become associated with it. Again, the solutions from Examples 2 and 3 were shown to have an improvement over the neat oil as less oil was associated with these cuttings.

EXAMPLE 7

[0032] Microemulsions have been prepared in the following base oil types:

[0033] i) paraffinic

[0034] ii) naphthenic

[0035] iii) linear alpha olefins

[0036] iv) ester type base fluids

EXAMPLE 8

[0037] A microemulsion using linear alpha olefin was prepared as in Example 2 using 35 parts of the surfactant composition. This was then tested using the lubricant industry standard IP287 to determine the potential of the solution to promote corrosion. No corrosion has been observed using this or indeed any other prepared solution.

EXAMPLE 9

[0038] The solution from Example 8 was doped with a heavily contaminated soluble oil. The resulting solution was then tested using an agar dipslide to monitor bacterial growth within the solution. No culture or bacterial growth was observed after 168 hours at 35° C. It is generally recognised that bacteria will be observed on the culture medium after 72 hours when held at 35° C.

EXAMPLE 10

[0039] Solutions from Examples 2, 3 and 8 have been tested for wear prevention using a Reichert testing machine. This involves rotating a roller bearing over a known distance (100 m) within a specific length of time (60 s) with a load of 1.5 Kg. When comparing the solutions with their respective straight oils a reduction in weight loss of 22% was observed on the solutions from Examples 2 and 3 whilst that of Example 8 showed a reduction in weight loss of 14%.

EXAMPLE 11

[0040] A hydraulic oil was prepared using the microemulsion from example 2 with an anti-wear additive based on sulphur. This was added at a rate of 5% v/v. A further hydraulic oil was prepared using the same base oil and sulphur additive. Both oils were then tested for their anti-wear properties using the Reichert testing apparatus. The microemulsion showed a reduced weight loss compared to the standard oil of 10%.

EXAMPLE 12

[0041] A gear oil has been prepared using a commercially available oil (Mobil Glygoyle HE460) and the composition of Example 1. The resulting oil has shown improved coolancy with no loss in lubricity using standard anti-wear tests i.e. four ball tests.

EXAMPLE 13

[0042] A grinding oil was prepared using a linear alpha olefin base oil with the composition of Example 1. This was tested against a standard grinding oil and was shown to be of superior cooling ability with no loss in lubricity. TABLE 1 Oil on Tool Diameter/ Speed/ Cut/ Length of Swarf Sample Number mm RPM mm cut/mm g/Kg Shell 130 1 75-60 140 2.5 600 8.0 solvent 60-45 190 2.5 600 neutral 45-25 260 2.5 600 25-20 350 2.5 600 As above + 2 75-60 140 2.5 600 8.3 1% 60-45 190 2.5 600 Cereclor 45-25 260 2.5 600 E45 25-20 350 2.5 600 Solution 3 75-60 140 2.5 600 6.1 from 60-45 190 2.5 600 Example 3 45-25 260 2.5 600 25-20 350 2.5 600 Solution 4 75-60 140 2.5 600 5.5 from 60-45 190 2.5 600 Example 2 45-25 260 2.5 600 25-20 350 2.5 600 As above + 5 75-60 140 2.5 600 5.6 1% 60-45 190 2.5 600 Cereclor 45-25 260 2.5 600 E45 25-20 350 2.5 600 

1. A composition for preparing a microemulsion of oil and water, the composition comprising i) a fatty acid amine ethoxylate ii) C₆-C₁₅ alcohol ethoxylate; and optionally iii) tall oil fatty acid amine
 2. A composition according to claim 1 which comprises the following i) 1-5 parts of a fatty acid amine ethoxylate ii) 0.5-4 parts of a C₆-C₁₅ alcohol ethoxylate; and optionally iii) 1.5-5 parts tall oil fatty acid amine
 3. A composition according to claim 1 or claim 2 comprising 3 parts of component (i) and 2 parts of component (ii) and optionally 2.75 parts of component (iii).
 4. A composition according to claim 1 or claim 2 comprising 3 parts of component (i) and 1 part of component (ii) and optionally 1.5 parts of component (iii).
 5. A composition according to claim 1 or claim 2 comprising 2 parts of component (i) and 1 part of component (ii) and optionally 3 parts of component (iii).
 6. A process comprising adding to a mixture of oil and water a surfactant composition according to any of claims 1-5 such that a clear homogenous microemulsion is formed. 